1. Field of the Invention
This invention relates to a method and apparatus for recording information signals and related secondary signals in parallel tracks on a magnetic recording medium. In particular, it relates to a method and apparatus for recording one set of main and secondary signals on a first main and a first secondary track parallel to each other and spaced apart from each other and interleaved with a second main and a second secondary track on which a second information signal and a second related signal is recorded, respectively. The secondary track related to a second main track is recorded between the first main track and the first secondary track related thereto, so that both secondary tracks are between their related main tracks.
2. The Prior Art
In certain types of magnetic tape equipment, a main signal is recorded simultaneously with a secondary signal. The secondary signal is frequently referred to as a control signal and contains control information, such as pulses corresponding to blocks of information in the information signals to allow a counting mechanism to count the number of such pulses in order to move the tape to desired locations thereon to pick up information recorded at such locations. Due to the fact that the secondary signals contain relatively little information, they do not require as much tape width as the main signals recorded simultaneously.
In some conventional tape recorders the control signals are recorded in very narrow tracks at the edges of the tape. Each main signal and the control, or secondary, signal associated therewith are recorded on slightly less than one half the total tape width with the tape moving in one direction. The other half of the tape has another main signal and another control signal recorded on it with the tape moving in the opposite direction. The arrangement of recording tracks in which the signals are recorded is symmetrical about the center line of the tape. As a result, if the moving tape fluctuates a small amount in the transverse direction while it is being pulled in the longitudinal direction, the pick up head that should respond to the narrow track of the recorded control signals may be shifted away from that track, thus making the control track operation unstable. To make matters worse, the head may disengage entirely from the track. This causes some of the signals to be dropped out, and in the case of control signals that are to be counted, this has an unacceptable influence on the count.
It has been proposed, in order to overcome the disadvantage of losing contact with the control tracks, to place the control tracks near the center of the tape. As before, one-half of the tape is used to record one main intelligence signal and its corresponding secondary, or control, signal while the tape moves in one direction and the other half is used to record a second main intelligence signal and its related secondary signal when the tape is moved in the other direction. The two control signals are recorded adjacent each other and the main signals are recorded in broader tracks near the outer edges of the tape. However, this still produces cross-talk between each of the main information signals and the respective secondary signals because each pair of main and secondary signals is spaced only a very short distance apart. In addition, the magnetic head to accomplish such spacing is difficult to construct because the part that records the second signal must be relatively close to the part that records the main signal.